Essentially all objects emit or radiate energy. Electromagnetic (EM) spectrum is a name often given to a number of types of radiation as a group. Radiation is energy that travels and spreads out as it travels away from the source; visible light that comes from a lamp and radio waves that come from a radio station are two types of electromagnetic radiation. Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays. Hotter, more energetic objects and events create higher energy radiation than cool objects.
Natural objects radiate EM energy that can be classified as Gaussian, while man-made objects radiate EM energy that is non-Gaussian. Gaussian energy can be defined as normally distributed (with a bell-shaped curve) and having a mean at the center of the curve with tail widths proportional to the standard.
It is well known that these EM energy signals can be collected using a receiver and used for identification and tracking purposes. This process is generally referred to as Specific Emitter Identification (SEI). Specific Emitter Identification is a method of recognizing individual electronic emitters through the precise measurement of selected signal externals (parameters and/or characteristics). In order to be identified by SEI techniques, a specific emitter must have one or more of these signal externals that are stable and that are unique within the measurement capabilities of most collectors. SEI can provide reliable and timely intelligence data for keeping track of individual target emitters and the particular units operating them.
Known SEI methods are generally based on the concept of identifying one or more characteristic radio signals that are unique to specific electrical devices used on or by objects of interest, and which can then be used to identify and track the objects having these devices. This prior art method requires a “library” or “database” of signals unique to specific electrical devices on objects of interest and which are compared against using the received signal to identify the object of interest. The characteristic signal of the object of interest must be stable and unique within the measurement capabilities of the collector/receiver. For example, a library or database may be developed of signals for specific devices that are to be identified and tracked such as missiles, aircraft, tanks or the like.
One of the problems associated with the known SEI methods is that objects often emit a wide range of radio signals, much of which cannot be used for identification purposes. Additionally, and most importantly, there are often many other objects in the area of interest that are also emitting radio signals or other EM energy that are generally collectively referred to as “background clutter” or “noise”. These “background clutter” or “noise” tend to mask or hide the signals of the objects of interest and make it difficult to identify and distinguish the object(s) of interest from the background clutter. Many of these “background clutter” or “noise” signals emanate from natural objects and not man-made objects and therefore, are not of interest.
Because of wide range of radio signals or other EM energy that are emitted, known SEI methods look for one or more specific signal which can be correlated to a particular known object, for example, a characteristic signal corresponding to a specific type of jet aircraft, missile, tank or the like. Unfortunately, the particular signal to be received and analyzed must be determined ahead of time in order for the known SEI methods to work. Such signals must be stored in a table, library, database or other reference source against which the received signal is compared for identification purposes. If the system/method does not know what signal to look for or cannot find a “match” in the reference library or database, then it will not be able to identify and/or track the object. Since the known SEI methods are limited to a specific signals, they are also not capable of simultaneously tracking/identifying multiple types of different objects.
Known SEI methods generally involve the use of two or more radio signal receiving platforms moving in different directions (preferably in generally perpendicular directions) along a geographical area of interest. As these radio signal receiving platforms move or pan for signals across the geographical area of interest, they form a grid having a plurality of quadrants or tiles.
According to the known SEI methods, these radio signal receiving platforms analyze a single, specific radio signal known to be indicative of specific targets (such as a personal transport, battle ship, an aircraft, troops, or the like), commonly referred to as a characteristic signal. Unfortunately, these methods are limited in that the methods can only detect objects that have been preprogrammed to look for; i.e., the method can only receive and analyze a specific signal that is characteristic of an object. Thus, if an object (for example, a particular type of tank or the like) is in the geological area of interest, and the characteristic signal for that particular tank has not be preprogrammed (in a database, table or the like) to be searched for, the known SEI methods will not detect the tank. Consequently, the tank may be allowed to move about within the geological area of interest undetected thereby significantly reducing the level of safety.
Accordingly, what is needed is an apparatus and/or method of identifying and/or tracking a wide range of objects within a geographic area of interest. The apparatus/method should not be limited to scanning for specific known or predetermined signals. Additionally, the apparatus/method should not need to previously know what emitter signal or signals to look for. The apparatus/method should also be capable of simultaneously tracking a number of multiple different types of objects.